2. Harmful Effects of weeds

3. Contents What is weed ? Competition for mineral nutrients
Competition for water
Competition for solar energy
Competition for space
Reduce the crop quality and quantity
Impair the quality of the animal produce
Harm animal health

4. Continue……… Harbor insect pest and diseases Damage human health
Competition for solar energy
Contaminate water bodies
Quicker wear and tear to farm implements
Reduce the value of land
Less efficient use of land
Increase in cost of cultivation
Disturbance in public places

5. What is weed?
Any plant which is out of its proper place is called weeds
Types of weeds
Annual weeds
Biennials
Perrineals
e.g wheat weeds, rice weeds, sugarcane weed

6. Weeds in wheat
Dumbi sitti
P. Minor

7. Competition for mineral nutrients
Being hardy and vigorous in growth habit; they soon outgrow the crops and consume large amount of water and nutrients. 
In general, weeds removed N and K from soil in much greater quantity than P.

8. Competition for water
Weeds consume large amount of water as compared to other crop plants
For producing equal amount of dry matter, the weeds, in general transpire more water than most crop plants e.g. wild mustard transpires about four times more water than a crop of oat.

9. Competition for Solar Energy
About 99% of dry matter in plants is made up of organic matter that is dependent on solar energy.
When plants are mutually shaded, their production potential is greatly reduced even though water and other nutrients are available to them in abundance.
Emerging plants are shaded by quick growing weeds

10. Competition for space
Weeds compete for space both in the rhizo sphere and atmosphere. In the presence of weeds, crop plants also have limited space to develop their shoots, which amounts to reduced photosynthesis in them.
More seed production of weeds
Growth habits of weeds

11. reduce the crop quality
Weeds may reduce the quality of the crop produce in many ways.
Weed seed like wild mustard, sweet clover, a Mexican poppy and bulblets of wild garlic and wild onion when threshed and ground with winter grains can results in serious consequences besides imparting objectionable odour to the flour. 

12. impair the quality of the animal produce
Many weeds in pastures and forage crops impart undesirable flavors to milk and meat of animals.
For e.g. Pivali tilwan (Cleome viscosa) imparts undesirable flavour to milk.
Gokharu or Landaga (Xanthium strumarium) get attached to the body of sheep and seriously impair the quality of wool.

13. Harm animal health
Several weeds of grasslands and forage crops contain high alkaloids, tannis, oxalates, gulcosides, and other substances that prove poisonous to animals when ingested.
For e.g. Silky lupine ( Lupinus sericeus) is responsible for crooked calf disease.
Some weeds are noxious and produce poisonous chemical which are injurious to animal health

14. Harbor insect pests or diseases
Weeds either give shelter to various insect pests and diseases or serve as alternate host. For e.g. Weed around paddy bunds harbour the gallfly.
Weeds act as a host
Cause of many diseases

15. Damage human health
Health, comfort and work efficiency of man are also affected by weeds directly or indirectly.
For e.g. people in U.P. are plagued year after year with hay fever and asthma aggravated by pollens of rag weeds.
Lantana flower leaves are dangerous for humans.

16. Contaminate water bodies
Aquatic weeds change the flavor appearance and taste of drinking water. Aquatic weeds are a menace to fisheries too. Aquatic weeds on decomposition gives offensive odors and pollute atmosphere.

17. Himalayan balsam
Himalayan balsam grows fast and can reach two to three metres in height. It rapidly spreads on the banks of slow-moving watercourses and becomes dominant, stopping other plants growing.

18. Quicker wear and tear to farm implements
Being hardy and deep-rooted, the tillage implements get worn early.

19. Reduce the value of the land
Agricultural lands heavily infested with perennial weeds like Kans (Saccharum spontaneum) always fetch less price.
Giant hogweed

20. Less efficient use of land
In case of perennial weeds, the carrying capacity of the grazing lands is reduced and cause depreciation of land value.

21. Increase in cost of cultivation
In fields of crops infested with weeds, the tillage operations require high cost.

22. Disturbance in Public places
It is desirable that public places be kept clean of weeds.
Presence of weeds around our living and working places makes the surroundings dull.

24. Any Question